Magnetic memory device and method of magnetic domain wall motion

ABSTRACT

A magnetic memory device comprises a first electrode, a second electrode, a laminated structure comprising plural first magnetic layers being provided between the first electrode and the second electrode, a second magnetic layer comprising different composition elements from that of the first magnetic layer and being provided between plural first magnetic layers, a piezoelectric body provided on a opposite side to a side where the first electrode is provided in the laminated structure, and a third electrode applying voltage to the piezoelectric body and provided on a different position from a position where the first electrode is provided in the piezoelectric body.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Division of application Ser. No. 13/282,605 filedOct. 27, 2011 the entire contents of which are incorporated herein byreference.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2011-076416, filed on Mar. 30,2011 the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein are related to a magnetic memory device,magnetic memory apparatus, and method of magnetic domain wall.

BACKGROUND

“A memory device, a selection device, and a wire which readsinformation” were fabricated in a semiconductor device. On the contrast,shift resistor type memory has been proposed for realizing a largecapacity memory. This idea is based on arraying only the memory devicesfor realizing high density memory, and this idea is a method fortransferring memory information to a sensor and a wire which are formedin given place. Thus, this idea enables memory capacity to increasemarkedly. The shift resister memory which is equipped with controlelectrode for each bit (digit) is not good as the use of memory, andseveral digits of shift motion should be operated by the shift resistermemory by applying some actions to whole bit lines. However it is noteasy for the shift resister to send whole digit information correctly.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of this disclosure will become apparent upon reading thefollowing detailed description and upon reference to the accompanyingdrawings. The description and the associated drawings are provided toillustrate embodiments of the invention and not limited to the scope ofthe invention.

FIG. 1 is a schematic view showing a cross section of a magnetic memorydevice of a first embodiment.

FIGS. 2A, 2B, and 2C are views showing an example of sequences ofmagnetic domain wall motion of a magnetic memory device of a firstembodiment.

FIGS. 3A, 3B, and 3C are views showing an example of sequences ofmagnetic domain wall motion of a magnetic memory device of a firstembodiment.

FIGS. 4A and 4B are views showing an example of sequences of magneticdomain wall motion of a magnetic memory device of a first embodiment.

FIG. 5 is a view showing an example of sequences of magnetic domain wallmotion of a magnetic memory device of a first embodiment.

FIG. 6 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIG. 7 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIG. 8 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIGS. 9A and 9B are schematic views showing a modified example of crosssection of a magnetic memory device and a piezoelectric body of a firstembodiment.

FIGS. 10A and 10B are schematic views showing a modified example ofcross section of a magnetic memory device and a piezoelectric body of afirst embodiment.

FIG. 11 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIG. 12 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIG. 13 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIG. 14 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIGS. 15A and 15B are schematic views showing a modified example ofcross section of a magnetic memory device and a piezoelectric body of afirst embodiment.

FIGS. 16A and 16B are schematic views showing a modified example ofcross section of a magnetic memory device and a piezoelectric body of afirst embodiment.

FIG. 17 is a schematic view showing a modified example of cross sectionof a magnetic memory device of a first embodiment.

FIG. 18 is a schematic view showing a magnetic memory device in a secondembodiment.

FIGS. 19A, 19B, and 19C are views showing an example of sequences ofmagnetic domain wall motion of a magnetic memory device of a secondembodiment.

FIGS. 20A, 20B, and 20C are views showing a simulation result of amagnetic memory device of a second embodiment.

FIG. 21 is a view showing a block circuit of a third embodiment.

FIG. 22 is a schematic view showing a block of a third embodiment.

FIG. 23 is a schematic view showing memory tip of an embodiment.

FIG. 24 is a view showing a block circuit of a first modified example ofa third embodiment.

FIG. 25 is a schematic view showing a block of a first modified exampleof a third embodiment.

FIG. 26 is a schematic view showing a block of a second modified exampleof a third embodiment.

FIG. 27 is a view showing a block circuit of a fourth embodiment.

FIG. 28 is a schematic view showing a block of a fourth embodiment.

FIG. 29 is a block circuit showing a first modified example of a thirdembodiment.

FIG. 30 is a schematic view showing a first modified example of a thirdembodiment.

FIG. 31 is a schematic view showing a second modified example of a thirdembodiment.

DETAILED DESCRIPTION

Embodiments will be described below with reference to drawings. Whereverpossible, the same reference numerals or marks will be used to denotethe same or like portions throughout figures, and overlappedexplanations are omitted in embodiments following a first embodiment.

First Embodiment

FIG. 1 shows a schematic view showing a cross section of a magneticmemory device of a first embodiment. The magnetic memory device I isprovided on a substrate, and the magnetic memory device 1 comprises afirst electrode 11, a second electrode 12, a third electrode 13, alaminated structure 14, a piezoelectric body 15, a writing section 16,and a reading section 17.

The laminated structure 14 comprises multilayer that a first magneticlayer 141 and a second magnetic layer 142 are laminated alternately, andthe laminated structure 14 is formed like a wire between the firstelectrode 11 and the second electrode 12. The second magnetic layer 142can be formed in contact with the first electrode 11 although the firstmagnetic layer 141 is formed in contact with the first electrode 11 inFIG. 1 A cross sectional shape cutting the first magnetic layer 141 andthe second magnetic layer 142 in laminating direction, which correspondsto z-direction in FIG. 1 and is also called as z-direction, isrectangular shape, for example. The cross sectional shape is not limitedfor the rectangular shape, but the cross sectional shape is notable tobe square, rectangle, polygon (hexagonal shape, for example), circle,ellipse, rhombus, or parallelogram. Aspect ratio of these shapes is from1 to 1 to 1 to 4. The first magnetic layer 141 and the second magneticlayer 142 are comprised of different composition of constituent elementeach other. Magnetostriction constant of the first magnetic layer 141has different sign from magnetostriction constant of the second magneticlayer 142. Or absolute value of the magnetostriction constant of thefirst magnetic layer 141 is smaller than the magnetostriction constantof the second magnetic layer 142 in the case where sign of themagnetostriction constant of the first magnetic layer 141 is differentfrom sign of the magnetostriction constant of the second magnetic layer142.

In-plane size, referring to a size which is parallel to z-direction, ofthe first magnetic layer 141 and the second magnetic layer 142 ismarkedly equal to or less than 100 nm not to generate inhomogeneousdistribution of magnetization direction. Bit data is memorized asmagnetization direction of given distance in the laminated structure 14of the magnetic memory device in laminating direction. Typically one bitdata per one first magnetic layer is reserved. Two or more bits data canbe reserved in the magnetic memory device. However, one bit data per onefirst magnetic layer is reserved following description.

In FIG. 1 and following schematic figures, only several of the firstmagnetic layers 141 and the second magnetic layers 142 are shown in thelaminated structure 14. However actual laminated structure 14 comprisesmuch more the first magnetic layers 141 and the second magnetic layers142 to be able to reserve from 100 bits data to several thousands data.The longer the whole length of the laminated structure 14 is, thelaminated structure 14 can comprise more the second magnetic layers 142and reserve a lot of bits data. However, the whole length of thelaminated structure 14 is typically from 100 nm or more to 10 μm orless.

As mentioned above, the laminated structure 14 comprises a lot ofmagnetic domains, corresponding to bit data which is reserved in themagnetic memory device, in the laminated structure 14. At the border oftwo neighbouring magnetic domains, magnetization direction changes inlaminating direction continuously. This changing region in magnetizationdirection is called magnetic domain wall. The magnetic domain wall has afinite width ‘w’ which is determined by the anisotropic energy orexchange stiffness of magnetic material.

The magnetization direction is not uniform in one first magnetic layer141 when current is not applied to the laminated structure 14. Thus, themagnetic domain wall generates near the boundary between the firstmagnetic layer 141 and the second magnetic layer 142 when themagnetization directions of two first magnetic layers 142 sandwichingthe second magnetic layer 142 are different. The width of the magneticdomain wall ‘w’ is described as w=(A/Ku)^(1/2). As typical value, A=1μerg/cm, K=10⁷ erg/cm³, and w=3 nm. The magnetic domain wall can becontrolled easily in the second magnetic layer 142 when each layerthickness of the second magnetic layer 142 is larger than the width ofthe magnetic domain wall ‘w’ and is twice as small as the width of themagnetic domain wall ‘w’. The magnetic memory device 1 enables toincrease the ratio accounting for the magnetic layer 141 in thelaminated structure 14. Thus the magnetic memory device 1 enables toincrease the amount of memory information if the laminated structure 14is regarded as the memory area in memory device. Each thickness of thefirst magnetic layer 141 is needed to be larger than the width of themagnetic domain wall ‘w’. If the thickness of the first magnetic layer141 is third times larger than the width of the magnetic domain wall,the volume of the area except for the magnetic domain wall is twicelarger than the volume of the area of the magnetic domain wall, and themagnetization state can be reserved easily even if the magnetic domainwall exists in the first magnetic layer 141.

The magnetization direction of the first magnetic layer 141 and themagnetization direction of the second magnetic layer 142 neighboring thefirst magnetic layer 141 are substantially parallel or antiparallel toeach other except for the area of the magnetic domain wall when voltageis not applied to the piezoelectric body 15.

A piezoelectric body 15 is provided on prolonged line which connectsplural of the first magnetic layers 141 and the second magnetic layers142. For example, in FIG. 1 the piezoelectric body 15 is providedbetween the first electrode 11 and the third electrode 13. One face ofthe piezoelectric body 15 is connected to the face opposite to the facewhere the first electrode 11 is connected to the laminated structure 14.The face, opposite to the face where the piezoelectric body 15 isconnected to the first electrode 11, is connected to the third electrode13.

Voltage can be applied between the first electrode 11 and the thirdelectrode 13. A current source, which is not shown in figure, isconnected between the first electrode 11 and the second electrode 12 andthe current source enables to pass current in the laminated structurebi-directionally.

A writing section 16 comprises a nonmagnetic layer 161 and aferromagnetic layer 162, and an electrode 163 and is connected to thelaminated structure 14. A signal source, which is not shown in figure,is connected to the electrode 163. Voltage is applied to the electrode163 from the signal source in order to write information in the magneticmemory device 1. In that case, spin-polarized electron flow passes inmagnetization direction of the ferromagnetic layer 162 when electronpasses from the electrode 163 to the laminated structure 14. Thespin-polarized current flow makes the magnetization direction of thelaminated structure 14 changed.

A reading section 17 comprises a nonmagnetic layer 171, ferromagneticlayer 172, and an electrode 173 and is connected to the laminatedstructure 14. In the case where the magnetization direction of themagnetic domain being connected with the reading section 17 of thelaminated structure 14 is orientated in the same direction (parallel) tothe magnetization direction of the ferromagnetic layer 172, alow-resistive state is generated between the electrode 173 and thesecond electrode 172. In the case where the magnetization direction ofthe magnetic domain being connected with the reading section 17 of thelaminated structure 14 is orientated in the opposite direction(antiparallel) to the magnetization direction of the ferromagnetic layer172, a high-resistive state is generated between the electrode 173 andthe second electrode 12. Recorded information can be read by theseresistance changes.

The magnetic memory device 1 enables to move bit data which is reservedin the laminated structure 14 without changing the order of the bit databy using following the magnetic domain wall motion steps. Thus beforewriting action and reading action, given bit data can be read andwritten in given position by moving the magnetic domain wall position atsufficient distance preliminarily.

Steps which move the magnetic domain wall in the laminated structure 14of the magnetic memory device 1 at given distance in z-direction areexplained. These steps comprise two steps. First step (step 1) is a stepwhich passes current between the first electrode 11 and the secondelectrode 12 from time t1 to time t2 as shown in FIG. 2A. Second step(step 2) is a step which applies voltage between the first electrode 11and the third electrode 13 from time t2 to time t4.

When current is flown between the first electrode 11 and the secondelectrode 12 (step 1), current which flows in the laminated structure 14is spin-polarized. The spin-torque acts on the magnetization of thefirst magnetic layer 141 and the second magnetic layer 142 whichcomprise the laminated structure 14. For this reason, the magneticdomain wall in the laminated structure 14 moves. The direction of themagnetic domain wall motion is same as the direction of electron flow,which is opposite to the direction of current flow.

When voltage is applied between the first electrode 11 and the thirdelectrode 13 (step 2), electric field is generated in the piezoelectricbody 15 for the direction which connects first electrode 11 and thethird electrode 13. In this case, the piezoelectric body 15 extends inthe direction which connects the first electrode 11 and the thirdelectrode 13 when the direction of electric field is same as thedirection of polarization of the piezoelectric body 15. In contrast, thepiezoelectric body 15 shrinks in the direction which connects the firstelectrode 11 and the third electrode 13 when the direction of electricfield is opposite to the direction of polarization of the piezoelectricbody 15.

In this case, due to inverse-magnetostrictive effect, a magneticanisotropy is induced by the strain applying to the second magneticlayer 142 in the laminated structure 14. As a result, the magnetizationdirection of the second magnetic layer 142 changes from the state beforestarting the step 2.

As an example, the case, where the magnetization direction of the secondmagnetic layer 142 is oriented in the perpendicular direction(x-direction in FIG. 1) to z-direction by magnetocrystalline anisotropyor like before starting the step 2, is explained. In the case where themagnetostriction constant of the second magnetic layer 142 is positive,elastic energy increases in the perpendicular direction to laminatingdirection by tensile strain in z-direction. For this reason, themagnetization direction of the second magnetic layer 142 turns inparallel (z-direction) to the laminating direction, for example, becauseit is difficult for the magnetization of the second magnetic layer 142to be in x-direction magnetization direction of the second magneticlayer 142. In the case where the magnetization coefficient of the secondmagnetic layer 142 is negative, elastic energy increases in x-directionby compressive strain in z-direction. For this reason, the magnetizationdirection of the second magnetic layer 142 turns in z-direction, forexample, because it is difficult for the magnetization direction of thesecond magnetic layer 142 to be in x-direction.

When the strain is not applied to the laminated structure 14 after thestep 2, the magnetic anisotropy of the second magnetic layer 142 returnsto the state before the start of the step 2. Then, the magnetizationdirection of the second magnetic layer 142 turns to x-direction.

The strain corresponding to stretching of the piezoelectric body 15 bythe step 2 is not only applied to the second magnetic layer 142 but alsoto the first magnetic layer 141. However in this embodiment, the sign ofthe magnetostriction constant of the first magnetic layer 141 isdifferent from the sign of the magnetostriction constant of the secondmagnetic layer 142. Or the absolute value of the magnetostrictionconstant of the first magnetic layer 141 is smaller than the absolutevalue of the magnetostriction constant of the second magnetic layer 142even if the magnetostriction constant of the first magnetic layer 141 issame as the magnetostriction constant of the second magnetic layer 142.

For this reason, magnetization direction of the first magnetic layer 141is unchanged. The two cases are explained to explain this phenomenon.

In the first case where the sign of the magnetostriction constant of thefirst magnetic layer 141 is opposite to the sign of the magnetostrictionconstant of the second magnetic layer 142, the magnetization directionof the first magnetic layer 141 is unchanged because the elastic energyof the first layer decreases when the elastic energy increases in thex-direction of the second magnetic layer 142, for example.

In the second case where the absolute value of the magnetostrictionconstant of the first magnetic layer 141 is smaller than the absolutevalue of the magnetostriction constant of the second magnetic layer 142even if the magnetostriction constant of the first magnetic layer 141 issame as the magnetostriction constant of the second magnetic layer 142,the magnetization direction of the first magnetic layer 141 is unchangedbecause the absolute value of the elastic energy which generates in thefirst magnetic layer 141 is small in the case where the elastic energygenerates in x-direction of the second magnetic layer 142.

The case, where the magnetization direction of the second magnetic layer142 turns in z-direction by crystalline magnetic anisotropy and shapemagnetic anisotropy before the start of the step 2 is same as abovecases. In the case where the magnetostriction constant of the secondmagnetic layer 142 is positive, elastic energy generates in z-directionby tensile strain in z-direction. For this reason, the magnetizationdirection of the second magnetic layer 142 turns in x-direction, forexample, because it is difficult for the magnetization of the secondmagnetic layer 142 to be in z-direction. In the case where themagnetization coefficient of the second magnetic layer 142 is negative,elastic energy generates in x-direction by compressive strain inz-direction. For this reason, the magnetization direction of the secondmagnetic layer 142 turns in z-direction, for example, because it isdifficult for the magnetization direction of the second magnetic layer142 to be in z-direction.

The magnetization direction of the first magnetic layer 141 and thesecond magnetic layer 142 can be in x-direction or in z-direction beforethe start of the step 2. For example, when the magnetization directionof the first magnetic layer 141 is in x-direction, the magnetizationdirection of the second magnetic layer 142 is easily controlled at theaction of the step 2 because the magnetization direction of the secondmagnetic layer 142 can be in z-direction by applying the magneticanisotropy derived from the fine line shape of the laminated structure14.

The magnetic domain wall can move from a first edge ‘X1’ of the firstmagnetic layer 141 to a second edge ‘X2’ of the first magnetic layer 141by using the step 1 and the step 2 if the time duration (the time fromt1 to t2) executing the step 1 is set longer than the time that themagnetic domain wall moves from the first edge X1 to the second edge‘X2’. The step 2 is started before the magnetic domain wall reaches thesecond edge ‘X2’. The step 2 can be started before starting the step 1.Then, the step 2 is finished after finishing the step 1 (t2≦t4).

FIG. 2 shows an example for timing which executes the step 1 and thestep 2 in the case where the magnetic domain wall moves only through onefirst magnetic layer 141. In FIG. 2 the step 1 is executed duringexecuting the step 2 (t3≦t1≦t2≦t4). Thus, the magnetic domain wall canbe stopped, before the second magnetic layer 142 if the step 2 isexecuted before starting the step 1 and after finishing the step 1. Asshown in FIG. 2C, the magnetic domain wall stops at the second edge ‘X2’at the time executing the step 1 and the step 2 simultaneously becausethe magnetic domain wall can propagate in the first magnetic layer 141and cannot propagate in the second magnetic layer 142.

FIG. 3 shows an example for timing which executes the step 1 and thestep 2 in the case where moving distance of the magnetic domain wall islonger than the case of the FIG. 2. The moving distance can becontrolled by changing the time from starting the step 1 to starting thestep 2. In FIG. 3 the magnetic domain wall moves through two firstmagnetic layer 141 and one second magnetic layer 142. For achievingthis, the step 2 is executed, after the magnetic domain wall passesthrough the first of the first magnetic layer 141 and the first of thesecond magnetic layer 142 and reaches at the border ‘X2’ between thefirst of the second magnetic layer 142 and the second of the firstmagnetic layer 141 after starting the step 1 and before the magneticdomain wall reaches at the border ‘X4’ between the second of the firstmagnetic layer 141 and the second of the second magnetic layer 142.

In FIG. 2 and FIG. 3 current and voltage are constant in the case of thestep 1 and the step 2. However the current value passing between thefirst electrode 11 and the second electrode 12 can be changed in thecase of the step 1, and the voltage value applying between the firstelectrode 11 and the third electrode 13 can be changed in the case ofthe step 2. For example, as shown in FIG. 4 the current value and thevoltage value can be changed two steps. In the case where the currentvalue being flowed in the step 1 is not temporally constant, forexample, the transition time that the magnetic domain wall transits fromthe static state to the moving state can be shortened if the formercurrent intensity except for rising edge is larger than the latercurrent intensity. In the case where the given voltage value istemporally constant, for example, the magnetic anisotropy of the secondmagnetic layer 142 derived from the applied strain becomes larger if thelater voltage is larger than the former voltage. Then, the magneticdomain wall can be stably stopped.

FIG. 5 shows an example that the step 1 and the step 2 are repeatedrespectively (in the case of the FIG. 5, the repetition is three times).In the FIG. 5, a schematic view showing the distribution of themagnetization of the magnetic layer after the step 1 and the step 2 areexecuted. In this example, each position of the magnetic domain wallmoves on the distance corresponding to the length of the first magneticlayer 141 in laminating direction of the laminated structure 14 everytime the step 1 and the step 2 are executed. Thus, the distance from themagnetic domain wall to the successive magnetic domain wall is unchangedeven if the step 1 and the step 2 are executed repeatedly. Thisindicates that on the magnetic memory device 1 the data whose isreserved during the moving process of the magnetic domain wall is notlost even if the position of the magnetic domain wall is moved.

As explained above, executing the step flowing current between the firstelectrode 11 and a third electrode and the step flowing current betweena first electrode and a second electrode enables to control the movingdistance of the magnetic domain wall stably.

Materials of the magnetic layer 141, 142 and the piezoelectric body 15are explained. Several magnetic materials can be used for the firstmagnetic layer 141 and the second magnetic layer 142. For example, atleast iron (Fe), cobalt (Co), and nickel (Ni) are typical materials. Analloy related to these elements is also used for the typical materials.Furthermore, at least one of elements selected from manganese (Mn),chromium (Cr), and palladium (Pd) can be added to the alloy. As thesematerials are based, several magnetic characteristics are realized byadding nonmagnetic element to these materials. Permalloy (NiFe alloy)and CoFe alloy or like can be used as a material whose magneticanisotropy is not so high.

Current can be smaller when the magnetic domain wall is moved by spininjection current if the magnetization direction is in perpendicular tothe laminating direction of the laminated structure 14 (x direction inthe FIG. 1) rather than is in the laminating direction of the laminatedstructure 14 (z direction in the FIG. 1). In order for the magnetizationdirection to be perpendicular to the laminated structure 14, themagnetic anisotropy is needed to be large to overcome diamagnetic fieldbecause the diamagnetic field in the case where the magnetizationdirection is in orthogonal direction (short axis) to the laminatedstructure 14 is larger than the diamagnetic field in the case where themagnetization direction is in the direction of the laminated structure14. For this reason, it is notable to use material comprising largemagnetic anisotropy.

Following materials can be used for the material comprising largeuniaxial-magnetic anisotropy (Ku). At least one element selected fromiron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), and chromium (Cr)and at least one element selected from platinum (Pt), palladium (Pd),iridium (Ir), Ruthenium (Ru), and Rhodium (Rh) can be used for the largeuniaxial-magnetic anisotropy material. The value of theuniaxial-magnetic anisotropy can be controlled by adjusting thecomposition of the magnetic layer or crystalline arrangement inannealing.

Magnetic material that comprises hexagonal closed packing structure andperpendicular magnetic anisotropy to the laminating direction of thelaminated structure 14 can be also used for the large uniaxial-magneticanisotropy material. Metal comprising cobalt (Co) can be used for thesematerials. The other metal comprising the hexagonal closed packingstructure can also be used.

In the case where the laminating direction of the laminated structure 14is formed perpendicular to the substrate, it is needed for the easy axisof the magnetic anisotropy is in plane in order for the magnetizationdirection is in perpendicular to the laminated structure 14. Co, CoPt,and CoCrPt are used for material which comprises large magneticanisotropy and that the easy axis of the magnetic anisotropy is inplane. CoPt and CoCrPt can be used as alloy. These materials aremetallic crystalline whose c-axis of hexagonal closed packing structureis in plane. Furthermore, above any cases, additional elements can beadded.

In the case where the laminating direction of the laminated structure 14is formed parallel to the substrate (in the case where the laminatedstructure 14 is formed parallel in plane of substrate), it is needed forthe easy axis of the magnetic anisotropy to be perpendicular to theplane. Co and CoPt, that c-axis of hexagonal closed packing structure isperpendicular to the plane, FePt, multilayer of (Co/Ni), and TbFe can beused for realizing these. CoPt can be used as alloy. In the case ofusing TbFe,TbFe comprises perpendicular magnetic anisotropy if Tbcomposition is ranged from 20 atomic % to 40 atomic %. Furthermore,above any cases, additional elements can be added.

The laminated structure 14 is formed perpendicular to the substratebetter than the laminating direction of the laminated structure 14 isformed parallel to the substrate. This is because in this case thelength of the second magnetic layer 142 in the fine line direction canbe shorten and data amount in the laminated structure 14 can be larger.

The first magnetic layer 141 and the second magnetic layer 142 can becontrolled by adding additive elements. The magnetostriction constant ofthe magnetic material added Ni element shifts to negative directioncompared to the magnetic material without Ni element. The change amountof the magnetostriction constant of the magnetic material added Nielement depends on additive amount of Ni element. For example, by addingNi element to the magnetic material comprising positive magnetostrictionconstant, the magnetostriction constant can be smaller. Themagnetostriction constant can be almost zero by increasing additiveamount of Ni element. Thus, positive or negative magnetostrictionconstant magnetic material can be used for the second magnetic layer142. Positive magnetostriction constant magnetic material, added Nielement in order for the magnetostriction constant to be almost zero,comprising same material as the first magnetic layer 141 or differentfrom that of the first magnetic layer 141 can be used for the firstmagnetic layer 141. These compositions can fabricate the magnetic memorydevice in this embodiment. The magnetic material can be negativemagnetostriction constant by increasing content of Ni element. Thus, byadding Ni element to either the first magnetic layer 141 or the secondmagnetic layer 142, and forming positive magnetostriction constantmaterial to one of the first magnetic layer 141 and the second magneticlayer 142, and negative magnetostriction constant material to the othercan fabricate the magnetic memory device in this embodiment.

For another example, as method for shifting the magnetostrictionconstant to positive side, adding minute amounts of oxygen to themagnetic layer enables to control content of oxygen of the magneticlayer. Using this method enables to control small-negativemagnetostriction constant for the material comprising large-negativemagnetostriction constant and to form the material whosemagnetostriction constant is almost zero. For example, the materialwhose magnetostriction constant is almost zero can be realized as thefirst magnetic layer 141. Or, these materials can be also used for thefirst magnetic layer 141 and the second magnetic layer 142 in order tobe positive magnetostriction constant.

Rare earth and iron group transition element related alloy comprisingperpendicular magnetic anisotropy in the fine line direction can beused. As this alloy, GdFe, GdCo, GdFeCo, TbFe, TbCo, TbFeCo, GdTbFe,GdTbCo, DyFe, DyCo, or DyFeCo can be used for the first magnetic layer141 and the second magnetic layer 142.

Magnetic property, crystalline property, mechanical property, chemicalproperty or various properties can be adjusted by adding nonmagneticelement such as Ag, Cu, Au, Al, Mg, Si, Bi, Ta, B, C, 0, N, Pd, Pt, Zr,Ir, W, Mo, Nb, or H to these magnetic materials used for the magneticlayer can be controlled.

Piezoelectric body being single crystalline or uniaxial can be used forthe piezoelectric body 15 in order to be uniform strain applied to thelaminated structure 14. Potassium sodium tartrate (KNaC₄H₄O₆), zincoxide (ZnO), aluminum nitride (AlN), lead zirconium titanate(PZT(Pb(Zr,Ti)O₃)), zirconium titanate lanthanum lead (PLZT), crystal(SiO₂), lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃), lithiumtetraborate (Li₂B₄O₇), potassium niobate (KNbO₃), langasrte crystalline(La₃Ga₅SiO₁₄ or like), or potassium sodium tartrate tetrahydrate(KNaC₄H₄O₆4H₂O) or like can be used for the piezoelectric body 15. Onthe basis of these piezoelectric materials, additive elements can beadded in order to adjust property. The piezoelectric body 15 can bemultilayer of these materials.

The materials same as used for the first magnetic layer 141 can be usedfor the ferromagnetic layer 162, 172 in the writing section 16 and thereading section 17.

Nonmagnetic metal or insulating film can be used for the nonmagneticlayer 161, 171 of the writing section and the reading section 17. One ofthe elements selected from Au, Cu, Cr, Zn, Ga, Nb, Mo, Ru, Pd, Ag, Hf,Ta, W, Pt, and Bi or alloy comprising at least one of these elements canbe used for the nonmagnetic metal. The thickness of the nonmagneticlayer 161, 171 is the length so that magnetostatic coupling between theferromagnetic layer 162, 172 and the magnetic layer 141 can be small andis smaller than spin diffusion length of the nonmagnetic layer 161, 171.The thickness of the nonmagnetic layer 161, 171 is ranged from 0.2 nm to20 nm.

It is effective for the nonmagnetic layer 161, 171 to be used astunneling barrier layer for insulating material used for the nonmagneticlayer 161, 171 in order to gain large magnetoresistive effect. In thiscase, Al₂O₃, SiO₂, MgO, AlN, Bi₂O₃, MgF₂, CaF₂, SrTiO₃, AlLaO₃, Al—N—O,Si—N—O, nonmagnetic semiconductor (ZnO, InMn, GaN, GaAs, TiO₂, Zn, Te,or doped transition metal into these materials), or like can be used forthe nonmagnetic layer 161, 171. These compounds are not completelycorrect composition stoichiometrically, and can be luck or excess ofoxygen, nitrogen or, fluorine. The thickness of the nonmagnetic layer161, 171 comprised of this insulating material is raged from 2 nm to 5nm. In the case where the nonmagnetic layer 161, 171 is insulatinglayer, pinhole (PH) can be in the nonmagnetic layer 161, 171.

Fabrication process of the magnetic memory device will be explained. Themagnetic memory device 1 is fabricated by used of sputtering andlithography. The fabrication process of the magnetic memory device 1 isexplained as the following.

First, a silicon substrate is etched by use of a mask and the secondelectrode 12 is buried in the silicon substrate. Next, the firstmagnetic layer 141 is deposited on the silicon substrate where thesecond electrode 12 is buried. And, a nonmagnetic layer, a ferromagneticlayer, and a metal layer (can be used as electrode) are deposited on thefirst magnetic layer 141 in this order.

Next, the writing section 16 and the reading section 17 are formed byuse of a mask and etching from the metal layer to the nonmagnetic layerso that the surface of the magnetic layer of the first magnetic layer141 is uncovered.

Next, an insulating layer is deposited on the first magnetic layer 141and the metal layer of the writing section 16 and the reading section17. Then, an opening is formed by etching the insulating layer so thatthe part of the insulating layer is uncovered.

Next, the laminated structure 14 whose height is over the height of thewriting section 16 and the reading section 17 is formed by depositingthe second magnetic layer 142 and the first magnetic layer 141alternately. For example, the deposition repeat count is about 200layers.

Furthermore, the first electrode 11 is formed on the first magneticlayer 141, and the piezoelectric body 15 is formed on the firstelectrode 11, and the third electrode 13 is formed on the piezoelectricbody 15. Finally, the surround of the magnetic memory device is buriedby an insulating layer.

Modified Example

This embodiment can be used for any transformation. In the FIG. 1 andabove explanation, voltage is applied between the first electrode 11 andthe third electrode 13. However, as shown in FIG. 6 the piezoelectricbody 15 can be shrunk by applying voltage between the second electrode12 and the third electrode 13.

As shown in FIG. 7, some bits data can be stored in one first magneticlayer 141 if the thickness of the first magnetic layer 141 is enoughthick in the laminating direction (z direction).

Some concaves whose cross sectional area of the laminated structure 14are different from the other part of the laminated structure 14 can beprovided in the laminated structure 14 in the laminating direction (zdirection), at regular interval. If such area is provided, pinningpotential become higher for the magnetic domain wall and the magneticdomain wall is easy to be controlled.

As shown in FIG. 8, anisotropy of the second magnetic layer 142 can beeasily controlled by inverse-magnetostrictive effect because the secondmagnetic layer 142 is applied larger strain than the first magneticlayer 141 if the cross sectional area of the second magnetic layer 142is smaller than the first magnetic layer 141.

In the case where the cross sectional area of the second magnetic layer142 is differentiated by the distance from the piezoelectric body 15,the strain applying to the second magnetic layer 142 can be equalized ifthe thickness of the second magnetic layer 142 comprising small crosssectional area is larger than the thickness of the second magnetic layer142 comprising large cross sectional area.

The laminated structure 14 can be surrounded by the piezoelectric body15. FIG. 9A is a schematic view showing the cross sectional image of themagnetic memory device 5 being provided so that the laminated structure14 is surrounded by the piezoelectric body 15 in the axis of thelaminated structure 14. FIG. 9B is an upper view of the magnetic memorydevice 5. By providing the piezoelectric body 15 like this, thelaminated structure 14 can be applied strain uniformly when voltage isapplied between the third electrode 13 and a fourth electrode 13 a.

In FIG. 9 the piezoelectric body 15 is provided so that thepiezoelectric body 15 is contact with the laminated structure 14.However, as shown in FIG. 10 an insulator 20, such as an amorphous SiO₂,an amorphous Al2O3, can be formed between the laminated structure 14 andthe piezoelectric body 15.

FIG. 11 is an example showing that the laminated structure 14 is formedin parallel to a substrate. The third electrode 13 and the fourthelectrode 13 a is provided upper side and lower side of thepiezoelectric body 15, and electric field can be applied to the upperand lower of the laminated structure 14. In this case, the laminatedstructure 14 can be surrounded by the piezoelectric body 15 as shown inFIG. 12 showing a cross sectional image being cut on A-A line in thefigure. Or, as shown in FIG. 13 and FIG. 14, the piezoelectric body 15can be provided on only the upper side and the lower side of thelaminated structure 14.

FIG. 15 is a schematic view of the magnetic memory device 7 so that thelaminated structure 14 is surrounded by the piezoelectric body 15. FIG.15 is an example that shows the shape and position of the thirdelectrode 13 and the fourth electrode 13 a of the magnetic memory device5, shown in FIG. 9, are changed. In this example, each of the thirdelectrode 13 and the fourth electrode 13 a comprises a pillar shape.Electric field is applied in the direction orthogonal to the laminatingdirection of the laminated structure 14 if voltage is applied betweenthe third electrode 13 and the fourth electrode 13 a by the step 2,because the laminated structure 14 is provided in the plane positionconnecting from the third electrode 13 to the fourth electrode 13 a.

In this case, the operation is essentially the same as that in the casewhere electric field is applied in the laminating direction of thelaminated structure 14 mentioned above. The magnetization direction ofthe second magnetic layer 142 is in the orthogonal direction to thelaminated structure 14, and in the case where the magnetostrictionconstant of the second magnetic layer 142 is positive, for example, theelastic energy increases in the orthogonal direction to the laminatingdirection of the laminated structure 14 and the magnetization directioncannot keep the orthogonal direction to the laminating direction of thelaminated structure 14 and the magnetization direction results in beingin parallel direction to the fine line, by applying voltage so thatcompressive strain is applied between the third electrode 13 and thefourth electrode 13 a in the orthogonal direction to the laminatingdirection of the laminated structure 14. Thus, in this case, themagnetic domain wall can also be stopped at the second magnetic layer142 by use of the step 2. In this case, the third electrode 13 andfourth electrode 13 a can comprise different cross sectional arearespectively.

As shown in FIG. 16, the third electrode 13 and the fourth electrode 13a can be as formed in flat plate shape, plural laminated structures 14can be provided in a pair of the third electrode 13 and the fourthelectrode 13 a. In this case, the number of lines to select the thirdelectrode 13 and the fourth electrode 13 a can be diminished because thethird electrode 13 and the fourth electrode 13 a can be used commonlyfor the plural laminated structures 14. The selectivity of the laminatedstructure 14 is not lost even if the third electrode 13 and the fourthelectrode 13 a is used commonly for the plural laminated structures 14,because the magnetic domain wall motion does not generate even if theonly step 2 is executed.

As shown in FIG. 17, the first magnetic layer 141 and the secondmagnetic layer 142 can be provided on the both edges of the firstmagnetic layer 141, and the writing section 16 and the reading section17 are provided on the edges.

Second Embodiment

FIG. 18 is a schematic view of a cross sectional image of the magneticmemory device of the second embodiment. The same components as themagnetic memory device 10 of the first embodiment are shown by the samesign, and detail explanation is omitted. The magnetic memory device 10of the second embodiment comprises the laminated structure 14 a beingarrayed the second magnetic layer 142 and a third magnetic layer 143alternately in the place of plural second magnetic layer 142 of themagnetic memory device 1 of the first embodiment. The second magneticlayer 142 or the third magnetic layer 143 is provided between the firstmagnetic layers 141 of the laminated structure 14 a, and the secondmagnetic layer 142 is provided between a first phase of the firstmagnetic layer 141 and the first magnetic layer 141 which is near to thefirst phase, and the third magnetic layer 143 is provided between theopposite phase to the first phase and the first magnetic layer 141 whichis near to the opposite phase.

Each of the absolute value of the magnetostriction constant of thesecond magnetic layer 142 and the third magnetic layer 143 is largerthan the absolute value of the magnetostriction constant of the firstmagnetic layer 141, and the magnetostriction constant of the secondmagnetic layer 142 is opposite to that of the third magnetic layer 143.Hereinafter, for example, the embodiment will be described that the signof the magnetostriction constant is positive, and the sign of the thirdmagnetostriction constant is negative.

The steps that magnetic domain wall in the laminated structure 14 a ofthe magnetic memory device 10 is moved in the fine line direction atregular interval will be described. These steps comprise a step 1 thatcurrent is applied between the first electrode 11 and the secondelectrode 12 from the time t1 to the time t2 as shown in FIG. 19A, astep 2 that positive voltage is applied between the first electrode 11and the third electrode 13 from the time t3 to the time t4 as shown inFIG. 19B, and a step 3 that negative voltage is applied between thefirst electrode 11 and the third electrode 13 from the time t5 to thetime t6.

Current applied in the laminated structure 14 a is spin-polarized, andspin torque is applied to the magnetization of the first magnetic layer141, the second magnetic layer 142, and the third magnetic layercomprising the laminated structure 14 a when current is applied betweenthe first electrode 11 and the second electrode 12 by the step 1. Thus,the magnetic domain wall moves in the laminated structure 14 a. Themotion direction of the magnetic domain wall is the same direction asthe motion direction of electron. Thus, the motion direction of themagnetic domain wall is opposite to the current direction.

Electric field is generated in the direction connecting the firstelectrode 11 to the third electrode 13 in a piezoelectric layer 15 whenpositive voltage is applied between the first electrode 11 and the thirdelectrode 13 by the step 2. Then, in the case where the electric fielddirection is same as the direction of polarization of the piezoelectricbody 15, the piezoelectric layer 15 is extended in the directionconnecting the first electrode 11 to the third electrode 13. In the casewhere the electric field direction is opposite to the direction ofpolarization of the piezoelectric body 15, the piezoelectric body 15 iscompressed in the direction connecting the first electrode 11 to thethird electrode 13. The applied strain corresponding to this compressionis applied to the laminated structure 14 a through the first electrode11. In this case, magnetic anisotropy is induced by the applied straindue to the inverse-magnetosrtictive effect in the second magnetic layer142 and the magnetization direction of the second magnetic layer 142changes from the state before starting the step 2. Although the magneticanisotropy is also induced by the applied strain due to theinverse-magnetostrictive effect in the third magnetic layer 143, themagnetization direction of the third magnetic layer 143 does not changebecause the sign of the magnetostriction constant of the third magneticlayer 143 is opposite to that of the second magnetic layer 142. As shownin FIG. 19, in the case where the step 2 finishes before the completingtime of the step 1 (t4≦t2), the magnetic domain wall does not passthrough the second magnetic layer 142 at the time that the step 1 andthe step 2 are executed simultaneously although the magnetic domain wallpropagates in the first magnetic layer 141 and the third magnetic layer143. Thus, the second magnetic layer 142 works as stopping the magneticdomain wall motion during executing the step 2.

Electric field is generated in the piezoelectric layer 15 in thedirection connecting the first electrode 11 to the third electrode 13when negative voltage is applied between the first electrode 11 and thethird electrode 13 by the step 3. Then, in the case where the electricfield direction is same direction as the polarization direction of thepiezoelectric body 15, the piezoelectric body 15 extends in thedirection connecting the first electrode 11 to the third electrode 13.In the opposite case, the piezoelectric body 15 shrinks in the firstelectrode 11 to the third electrode 13. The applied strain correspondingto this shrinking is applied to the laminated structure 14 a through thefirst electrode 11. In this case, the magnetic anisotropy derived fromthe applied strain generates by the inverse-magnetostrictive effect inthe third magnetic layer 143 and the magnetization direction of thethird magnetic layer 143 changes from the state before starting the step3. Although the magnetic anisotropy derived from the applied strain alsogenerates by the inverse-magnetostrictive effect in the third magneticlayer 143, the magnetization direction of the third magnetic layer 143does not change because the sign of the magnetostriction constant of thethird magnetic layer 143 is opposite to that of the second magneticlayer 142. As shown in FIG. 19, in the case where the step 1 finishesbefore the completing time of the step 3 (t2≦t6), the magnetic domainwall does not pass through the third magnetic layer 143 at the time thatthe step 1 and the step 3 are executed simultaneously although themagnetic domain wall propagates in the first magnetic layer 141 and thesecond magnetic layer 142. Thus, the third magnetic layer 143 works as astopping layer where the magnetic domain wall stop moving duringexecuting the step 3.

As mentioned above, by executing the step 1 and the step 3, for example,as shown in FIG. 19C the magnetic domain wall can be moved from thefirst edge X1 of the first of the first magnetic layer 141 to the secondedge X4 of next first magnetic layer 141. As shown in FIG. 19C, to movethe magnetic domain wall from the first edge X1 of the first of thefirst magnetic layer 141 to the second edge X4 of the second of thefirst magnetic layer 141 sandwiching the second magnetic layer 142, thestart time and finish time of the step 1˜step 3 are set as below.

Thus, after start of the step 1, the step 1 finishes after the time thatthe magnetic domain wall reaches the second edge X4 of the second of thefirst magnetic layer 141. This enables the magnetic domain wall to reachstably the second edge X4 of the second of the first magnetic layer 141.After start of the step 1, the step 2 starts before the time that themagnetic domain wall reaches the second edge X2 of the first of thefirst magnetic layer 141. This prevents the magnetic domain wall frommoving ahead of the second magnetic layer 142. After start of the step1, the step 2 finishes after the magnetic domain wall reaches the secondedge X2 of the first of the first magnetic layer 141, and after the step2 finishes, the step 3 starts before the magnetic domain wall reachesthe second edge X4 of the second of the first magnetic layer 141. Thisenables the magnetic domain wall to move through the second magneticlayer 142. And this enables also to prevent the magnetic domain wallfrom moving ahead of the third magnetic layer 143.

As mentioned above, according to the magnetic memory device 10 of thesecond embodiment, when the magnetic domain wall moves through one ofthe second magnetic layer 142 and the third magnetic layer 143, themagnetic domain motion can be controlled stably because the otherprevents the magnetic domain wall from moving.

The step 2 and the step 3 can be executed plural times during executingthe step 1. The number of the times of executing the step 2 and the step3 can be determined corresponding to the number of first magnetic layer141 that makes the magnetic domain wall moved. The finish time of thestep 2 or the step 3 out of executing the step 2 or the step 3 pluraltimes which is executed at final is to be after the finish time of thestep 1. This enables the magnetic domain wall to move stably thedistance corresponding to plural of the first magnetic layers 141 duringgiven time.

The simulating result about the magnetic domain motion in the laminatedstructure comprising two second magnetic layers 142 and two thirdmagnetic layers 143 is shown in FIG. 20. The magnetization alignmentshown in the top area in the FIG. 20C is initial state. Current isapplied between the first electrode 11 and the second electrode 12(executing the step 1) on the basis of the timing chart shown in FIG.20A. Positive voltage and negative voltage are applied between the firstelectrode 11 and the third electrode 13 (executing the step 2 and thestep 3) on the basis of the timing chart shown in FIG. 20B. Thesimulating result in FIG. 20C shows that the second magnetic layerprevents the magnetic domain wall motion during executing the step 1 andthe step 2 simultaneously, and the third magnetic layer prevents themagnetic domain motion during executing the step 1 and the step 3simultaneously.

Third Embodiment

A block comprising the magnetic memory devices being aligned, a writingsection, and a reading section will be explained.

FIG. 22 is a schematic view of the block circuit of the thirdembodiment. FIG. 22 is a perspective view of the part of a block 50 ofthis embodiment. In the block of the third embodiment, a magnetic memorydevice R1 that the piezoelectric body is provided on the extending lineconnecting the first magnetic layer to the second magnetic layer is usedfor either of the magnetic memory devices explained in the firstembodiment or the second embodiment and modified example related to thefirst embodiment or the second embodiment. The block of the thirdembodiment comprises the magnetic memory device R1, a switching device T(this device is comprised of a transistor, for example), and a memorytrack array MTA that is aligned like matrix state of m rows and ncolumns (m and n are positive integers). FIG. 2 shows the part of thememory track array MTA and the state that the memory track of 4 rows 4columns is aligned.

A magnetic thin wire ML(i) (1≦i≦m) is comprised of each laminatedstructure, comprised of the n number of the magnetic memory devices R1of the i th row (1≦i≦m), connected to the first magnetic layer beinglocated at the edge of the laminated structure of neighboring magneticmemory device R1. the piezoelectric body 15 of the magnetic memorydevice R1 is provided between the magnetic thin wire ML(i) (i≦i≦m) andan electrode SL (for moving the magnetic domain wall) at every laminatedstructure. As mentioned above, in the case where the laminated structureof plural magnetic memory devices R1 is connected to the first magneticlayer, the electrode (the first electrode and the second electroderelated to the first embodiment or the second embodiment and themodified example related to these embodiments) for applying current tothe magnetic thin wire ML may not be provided at every magnetic memorydevice R1. Or the first electrode can be provided at one edge of themagnetic thin wire ML, the second electrode can be provided at the otheredge of the magnetic thin wire ML. The magnetic thin wire may not becomprised of the magnetic memory devices R1. that each magnetic memorydevice R1 is connected each other. The first magnetic layer of eachmagnetic memory device R1 can be connected directly to peripheralcircuit that will be mentioned.

The memory track array MTA comprises word lines WL (1)˜WL (m) which areprovided on each row, the electrode SL (1)˜SL (m) like line shape, andbit lines BL (1)˜BL (n) for reading information which are provide oneach column. Plural word lines WL are aligned parallel each other, andthe alignment of the electrode SL and the bit line is also same as thecase of the word line WL. When viewing from z axis of FIG. 22, theelectrode SL extends in the direction parallel to the word line WL, andthe bit line BL extends in the direction crossing the electrode SL andthe word line WL.

A gate of the switching device T of each memory track is connected tothe word line corresponding to each row, one edge of the gate isconnected to one edge of the reading section 17 of the magnetic memorydevice R in the memory track, and the other edge of the gate isgrounded. The other edge of the reading section 17 of the magneticmemory device R1 in the memory track is connected to the bit line BLcorresponding to the memory track mentioned above.

As shown in FIG. 21, the word lines WL (1)˜WL (m), the magnetic thinwire ML (1)˜ML (m), and the electrode SL (1)˜SL (n) are connected to adecoder selecting each line and drive circuit 410A, 410B comprising awriting circuit or like. The bit lines BL (1)˜BL (n) are connected to adecoder selecting each line and drive circuit 420A, 420B comprising areading circuit or like. In FIG. 21 and FIG. 22, the writing section ofthe magnetic memory device R1 is omitted and not shown. One edge of thewriting section can be connected to the switching device, not shown, forwriting and selecting, and the other edge of the writing section can bea current source, not shown. The switching device for writing and theswitching device for reading device can be used commonly for the writingselection. One reading section and one writing section can be providedfor the plural memory tracks. In this case, this enables to make ahigh-density integration. In contrast, in the case where one readingsection and one writing section are provided on each memory cell, thedata transfer speed can be high.

The magnetic domain wall motion in the memory track of this embodimentwill be explained. For example, as explained in the first embodiment,the magnetic memory device R1 comprises the laminated structurecomprised of the first magnetic layer and the second magnetic layer.Address signal inputted from the external is decoded by the decoder inthe drive circuit 410A, 410B, 420A, 420B, and the magnetic thin wire MLand the electrode SL corresponding to the address being decoded areselected, and the magnetic domain wall motion is executed (shift motionof data) by the step 1 applying current to this selected magnetic thinwire ML and the step 2 applying voltage to the electrode SL.

The step 1 and the step 2 are executed by using the timing explained inthe first embodiment. In the case where the magnetic memory device R1comprises the laminated structure comprised of the first magnetic layer,the second magnetic layer, and the third magnetic layer as explained inthe third embodiment, the step 1, the step 2, and the step 3 areexecuted by using the timing explained in the second embodiment.

As mentioned above, by using this method of the magnetic domain wallmotion in the memory track, the data position moves simultaneously inplural magnetic memory devices R1 included in the magnetic thin wire ML(i) comprising the magnetic thin wire ML (i) and existing on the samerow of the memory track array MTA. Thus, data motion can be executed byone current source when plural magnetic memory devices are connectedeach other by sharing the first magnetic layer being provided on theedge of the magnetic memory device and the other first magnetic layer ofthe magnetic memory device. For this reason, electric power of the wholememory track array MTA can be reduced. The direction of the magneticdomain wall motion is same direction as the direction of electroncurrent. Thus, the direction of the magnetic domain wall motion isopposite to the direction of electric current.

The writing to the memory track is executed when the decoder in thedrive circuit 410A, 410B, 420A, 420B decodes the address signal inputtedfrom the external part and the decoder chooses the word line WLcorresponding to the address which is decoded and the switching device Tis on. After that, data is written by applying current to the bit lie BLfor reading information. Or data is written after moving the datareserved in the magnetic thin wire ML. For example, continuous data canbe written fast when moving the distance corresponding to one bit andexecuting one bit data writing are executed alternately.

The data reserved in the memory track is read when the decoder in thedrive circuit 410A, 410B, 420A, 420B decodes the address signal inputtedfrom the external part and the decoder chooses the magnetic thin wire MLcorresponding to the address being decoded and the data is shifted byuse of above method so that the bit which is read is located on thereading section within bit column reserving the data in the memory trackas the magnetization direction. After that, data is read when thedecoder chooses the word line WL and sets the switching device T on andcurrent is applied to the bit line BL for reading information. Forexample, continuous data can be read fast when moving the distancecorresponding to one bit and executing one bit data reading are executedalternately. The direction of reading current can be positive ornegative direction. The absolute value of the reading current is smallerthan the absolute value of writing current. This enables the datareserved by the reading to prevent from inversion.

A memory tip can be formed when plural blocks 50 are used. FIG. 23 showsa schematic view of the memory tip that plural blocks 50 are used. Thememory tip can be formed by putting plural blocks on a tip.

Modified Example

FIG. 24 is a schematic view of a block circuit of the first modifiedexample of the third embodiment. FIG. 25 is a perspective view of a partof a block 51 of this modified example. In the case of the block 51, theextending direction of a line shape electrode SL for moving the magneticdomain wall (also called electrode SL) is different from that of theblock 50 shown in FIG. 22. In the case of the block 50, the electrode SLextends in the direction parallel to the word line WL viewing fromz-direction in FIG. 22. In the case of the block 51 of the firstmodified example the electrode SL extends in the direction (thedirection crossing in the word line) parallel to the bit line BL forreading information viewing from z-direction in FIG. 25. The detailcomposition other than the electrode SL is same as the block 50, thusthe detail explanation can be omitted.

The methods, the magnetic domain wall motion in the memory track of theblock 51, writing data to the memory track, and reading data reserved inthe memory track are same as the case of the method of the block 50.

FIG. 26 is a perspective view of a part of a block 52 of a secondmodified of the third embodiment. In the block 52, the piezoelectricbody 15 is shared with plural magnetic memory devices R1. As shown inFIG. 26, the piezoelectric body 15 is provided on the upper part of thelaminated structure of plural magnetic memory devices R1. Moreover, aplane shape electrode 15 is provided on the upper part of thepiezoelectric body 15. An insulator such as amorphous SiO₂, amorphousAl₂O₃ can be formed between the piezoelectric body 15 and the planeshape electrode 15, or between the laminated structure of the magneticmemory device R1 and the piezoelectric body 15. The detail compositionother than the piezoelectric body 15 is same as the block 50, thus thedetail explanation can be omitted.

In FIG. 26 an example that plane shape piezoelectric body 15 is providedon the upper part of the laminated structure of plural magnetic memorydevices R1 that are aligned to be matrix. However, the piezoelectricbody 15 and the electrode SL can be provided at every column or everyrow of the memory track array MTA. The piezoelectric body 15 can beprovided at every magnetic memory device R1 and the electrode can beprovided on (or sandwiching the insulator) plural piezoelectric bodies15.

Applied strain can be added to plural laminated structures when voltageis applied to the piezoelectric body 15 by use of the electrode SLbecause in the case of the block 52 in FIG. 26 the piezoelectric body 15is formed over the upper part of the laminated structure of pluralmagnetic memory devices R1. For example, the magnetic domain wall motioncan be controlled every block when the piezoelectric body 15 is formedover the part of whole block 52.

The word line WL, the bit line for reading information, the switchingdevice T of the memory track, and the drive circuit 410A, 410B, 420A,420B are an example. These position, shape, or composition can bechanged arbitrarily.

Fourth Embodiment

FIG. 27 is a schematic view of a block circuit of the fourth embodiment.FIG. 28 is a perspective view of a part of a block of the fourthembodiment. The magnetic memory device R2 is used for a block 60 of thefourth embodiment that the piezoelectric body surrounds the peripheralof the laminated structure of the magnetic memory device of the firstembodiment, the second embodiment, or the modified example. Thepiezoelectric body is provided on peripheral of the laminated structureof the magnetic memory device R2 comprising the magnetic thin wire ML(not shown in FIG. 28). An insulator such as an amorphous SiO₂ oramorphous Al₂O₃ can be formed between the laminated structure of themagnetic memory device R2 and the piezoelectric body. This enables tokeep insulation stably.

In the case where in FIG. 28 the magnetic thin wire ML is comprised ofplural magnetic memory devices R2 being connected each other asmentioned in the third embodiment, the first electrode can be providedon one edge of the magnetic thin wire ML and the second electrode can beprovided on the other edge of the magnetic thin wire ML for applyingcurrent to the magnetic thin wire ML. The first magnetic layer of eachmagnetic memory device R2 can be connected directly to peripheralcircuit. The word line WL of the block 60, the bit line for readinginformation, the switching device T of the memory track, and the drivecircuit 410A, 410B, 420A, 420B are same as the block 50 of the thirdembodiment. Thus, the detail explanation is omitted.

In the block 60 shown in FIG. 28, a plane shape electrode SL is providedbetween the magnetic thin wire ML and the other magnetic thin wire ML,and the plane shape electrode SL is aligned parallel to connectingdirection of plural magnetic memory devices R2 of the magnetic thin wireML. The shape of the electrode SL can be plane shape as shown in FIG. 28or can be the other shape. In FIG. 28 the pair of electrode SLneighboring each other that sandwiching one magnetic thin wire MLHowever, plural plane shape electrodes SL can be provided to sandwichwhole magnetic thin wire ML (i) (1≦i≦m).

For example, the plane shape electrode SL corresponds to the thirdelectrode 13 in FIG. 15 and the fourth electrode 13 a in FIG. 16. Thisplane shape electrode SL is a pair of electrodes SL neighboring eachother and sandwiching one magnetic thin wire ML (i) and has samefunction as one line shape electrode SL in FIG. 22.

Plane shape electrode SL is connected to the drive circuit 410A, 410Bvia line. This enables to select the pair of electrode SL and applyelectric field therein.

The magnetic domain wall motion in the memory track of this embodimentis same as the third embodiment. Thus, the decoder in the drive circuit410A, 410B, 420A, 420B decodes the address signal inputted from theexternal part, and the decoder selects the magnetic thin wire ML and apair of electrode SL corresponding to the address which is decoded, anda step 1 that current is applied to the magnetic thin wire ML which isselected and a step 2 that voltage is applied to the pair of electrodeSL are executed. These steps enable the magnetic domain wall to move(data shift motion). The step 1 and the step 2 are executed at thetiming explained in the first embodiment. In the case where the magneticmemory device R2 comprises the laminated structure of the first magneticlayer, the second magnetic layer, and the third magnetic layer asexplained in the second embodiment, the step 1 and the step 2 areexecuted at the timing of the second embodiment.

Writing data to the memory track and reading data reserved in the memorytrack are same as the method of the third embodiment.

As mentioned above, data shift motion can be also executed by onecurrent source in the fourth embodiment when the first magnetic layerbeing located on the edge of the magnetic memory device shares the othermagnetic memory device and plural magnetic memory devices are connected.For this reason, power consumption of whole the memory track array MTAcan be controlled. Thus, the direction of the magnetic domain wallmotion is opposite to the direction of electric current.

Large capacity memory tip can be fabricated as explained in the thirdembodiment by using plural blocks in the fourth embodiment.

Modified Example

FIG. 29 is a schematic view of a block circuit of the first modifiedexample of the fourth embodiment. FIG. 30 is a perspective view of apart of a block 61 of the modified example. In the fourth embodiment,the extending direction of plane shape electrode SL can be also changedsame as the first modified example of the third embodiment. In the block61 of the first modified example shown in FIG. 30, the electrode SLextends in the direction parallel to the bit line BL for readinginformation (the direction crossing in the word line WL). A pair ofelectrodes SL is provided in the block 61 every laminated structure thatthe first magnetic layer, the second magnetic layer, and the thirdmagnetic layer are laminated in z-direction of the magnetic memorydevice R2.

In FIG. 30, electrode SL for one laminated structure is only shown.However, plural electrodes SL can be provided to sandwich each laminatedstructure. The composition other than the electrode SL is same as thecase of the block 60, thus the detail explanation is omitted.

The magnetic domain wall motion in the memory track of the block 61,writing data to the memory track, and reading data reserved in thememory track are same as the case of the block 60.

FIG. 31 is a perspective view of a block 62 of a second modified exampleof the fourth embodiment. In the block 62 of the second modified exampleof the fourth embodiment, the pair of electrodes SL is provided tosandwich the laminated structure of whole memory track included in theblock.

In the case of the block 62 shown in FIG. 31, when a voltage is appliedto the piezoelectric body 15 being sandwiched by a pair of electrodesSL, a strain can be applied to the laminated structure being surroundedby the piezoelectric body 15 and the magnetic domain wall motion can becontrolled every block.

The pair of plane shape electrodes SL can be provided every pluralcolumn of the magnetic thin wire ML In this case, the number of theelectrodes SL shown in FIG. 21 is smaller than the m number of theelectrodes SL. This structure enables to decrease the area ratio of theelectrode SL occupied in whole memory track. Thus, this structure hasadvantage for high integration. On the other hand, for example, as shownin FIG. 28, in the case where the pair of electrodes SL is provided tosandwich one magnetic thin wire SL, selecting the magnetic thin wireexecuting the step 1 and the step 2 simultaneously becomes easier whenthe magnetic domain wall position is moved.

In the second modified example of the fourth embodiment, an example thatthe electrode SL is aligned parallel to the connecting direction ofplural magnetic memory device R2 in the magnetic thin wire. However, thefirst modified example and the second modified example can be combined.The electrode SL can be aligned in direction orthogonal to connectingdirection of plural magnetic memory devices R2 in the magnetic thin wireML. This enables a pair of plane shape electrode SL to be provided everyplural rows of the magnetic thin wire ML (i). The position that theelectrode SL is provided toward the piezoelectric body 15 can be changedarbitrarily if electric field can be applied to the piezoelectric body15.

The word line WL, the bit line for reading information, the switchingdevice T of the memory track, and the drive circuit 410A, 410B, 420A,420B shown in this embodiment and the modified example related to thisembodiment are an example. These position, shape, or composition can bechanged arbitrarily.

The embodiments related to this invention are explained by usingconcrete examples. However, this invention is not limited to theseembodiments. For example, concrete size of each element comprising themagnetic memory device, materials, electrodes, passivation, shape orcomposition related to insulating structure can be included in thisinvention if ordinary skill person execute this invention same as thisembodiments by selecting ordinary skill arbitrarily and can gain sameeffect from doing that. For example, for each magnetic layer comprisinga magnetic element, the shape and the size are not needed to be same, sothe shape and the size can be fabricated as different each other. Eachelement of antiferromagnetic layer, intermediate layer, and insulatinglayer or like comprising the magnetic memory device can be formed assingle layer or can be multiple layers that plural layers are laminated.The modified example explained in each embodiment can be applied toother embodiments or plural modified examples can be combined eachother.

In basis of the magnetic memory devices or the magnetic recording devicementioned above as the embodiment of this invention, whole magneticmemory device or recording device that ordinary skill person canfabricate and change and execute arbitrarily can be included in thisinvention if the ordinary skill person executes within the aim of thisinvention.

The word “perpendicular” includes gap generated from a perpendicularthat is derived from the variation of fabricating process. In the sameway, the meaning of “parallel”, “flat” are different from the meaning ofabsolute parallel or absolute flat.

While certain the embodiment of the invention has been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the embodiment of the inventions. Indeed,the novel elements and apparatuses described herein may be embodied in avariety of other forms; furthermore, various omissions, substitutionsand changes in the form of the methods and systems described herein maybe made without departing from the spirit of the embodiment of theinvention. The accompanying claims and their equivalents are intended tocover such forms or modifications as would fall within the scope andspirit of the embodiment of the invention.

What is claimed is:
 1. A magnetic memory device comprising: plurallaminated structures, each laminated structure comprising; plural firstmagnetic layers; and a second magnetic layer comprising differentcomposition elements from that of the first magnetic layer and beingprovided between plural first magnetic layers; a piezoelectric bodyprovided to surround the plural laminated structures; and a firstelectrode and a second electrode applying voltage to the piezoelectricbody.
 2. A magnetic memory system comprising a plurality of the magneticmemory devices according to claim 1, the magnetic memory devices beingaligned in a row direction or in a column direction.
 3. The magneticmemory device according to claim 1, wherein the first electrode and thesecond electrode are extended parallel to a row direction or a columndirection.
 4. The magnetic memory device according to claim 1, wherein asign of a magnetostriction constant of the first magnetic layers isdifferent from a sign of a magnetostriction constant of the secondmagnetic layer, or an absolute value of the magnetostriction constant ofthe first magnetic layers is smaller than an absolute value of themagnetostriction constant of the second magnetic layer.
 5. The magneticmemory device according to claim 1, wherein: the first magnetic layerand the second magnetic layer comprising GdFe, GdCo, GdFeCo, TbFe, TbCo,TbFeCo, GdTbFe, GdTbCo, DyFe, DyCo, or DyFeCo.
 6. A magnetic memorydevice comprising: plural laminated structures arranged in a rowdirection and a column direction, each laminated structure comprising:plural first magnetic layers; and a second magnetic layer comprisingdifferent composition elements from that of the first magnetic layer andbeing provided between plural first magnetic layers; a piezoelectricbody provided to surround the plural laminated structures; and a firstelectrode and a second electrode applying voltage to the piezoelectricbody.
 7. The magnetic memory device according to claim 6, wherein thefirst electrode and the second electrode are extended parallel to a rowdirection or a column direction.
 8. The magnetic memory device accordingto claim 6, wherein a sign of a magnetostriction constant of the firstmagnetic layers is different from a sign of a magnetostriction constantof the second magnetic layer, or an absolute value of themagnetostriction constant of the first magnetic layers is smaller thanan absolute value of the magnetostriction constant of the secondmagnetic layer.
 9. The magnetic memory device according to claim 6,wherein: the first magnetic layer and the second magnetic layercomprising GdFe, GdCo, GdFeCo, TbFe, TbCo, TbFeCo, GdTbFe, GdTbCo, DyFe,DyCo, or DyFeCo.
 10. A method of magnetic domain wall motion of themagnetic memory device of claim 1, comprising: a first step applying acurrent between the first electrode and the second electrode for a firsttime duration; and a second step applying a voltage to the piezoelectricbody for a second time duration, wherein a completing time of the secondstep is after a completing time of the first time.